Ink formulations, under the right conditions, ingest air and produce foam. These conditions include an air/ink interface where, for example, agitation produces foam. This air/ink interface can occur in storage bottles, as well as the printhead. Agitation can occur during shipment of the ink bottles or containers, and more likely, through the removal of the ink containers from the printer during service of the printer, when the ink types are changed, or during general movement of the printer.
In an inkjet printer, a robust ink delivery system is critical. Thus, the presence of foam can be a major problem, since it can eventually block the ink flow. Moreover, displacing foam from capillaries, such as ink delivery tubes, ink reservoirs and printheads can be extremely difficult.
In large format and high volume inkjet printers, it is desirable to use large volumes of ink, for example, greater than 1 liter/color resident in the printer. This typically requires one or more storage containers in addition to a complex delivery and pumping system to move the ink from the user-accessible ink bottles to the printhead. With such printers it is imperative that no foam is introduced into the delivery system.
One manner of reducing the production of foam is to reduce the air/ink interface within the container. This can be accomplished by filling the ink bottles to the maximum capacity. However, this only solves the problem in new ink containers. Once the containers are installed and the ink is consumed, the volume originally occupied by the ink is replaced with air, as the bottle must be open to the atmosphere for the ink delivery system to work properly.
Thus, it is desirable to reduce the amount of foam present in an ink container of a printer.